Identification and expression profile of a new cytochrome P450 isoform (CYP414A1) in the hepatopancreas of Venerupis (Ruditapes) philippinarum exposed to benzo[a]pyrene, cadmium and copper

Polystyrene microplastics alleviate adverse effects of benzo[a]pyrene on tissues and cells of the marine mussel, Mytilus galloprovincialis

As two major ubiquitous pollutants, microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) coexist in the marine environment. However, the role of MPs in altering the toxicity of PAHs to marine organisms is poorly understood. We therefore investigated the accumulation and toxicity of benzo[a]pyrene (B[a]P, 0.4 nM), in the marine mussel Mytilus galloprovincialis over a 4-day of exposure with or without the presence of 10 μm polystyrene microplastics (PS MPs) (10 particles/mL). The presence of PS MPs significantly decreased B[a]P accumulation in soft tissues of M. galloprovincialis by approximately 6.7%. Single exposure of PS MPs or B[a]P decreased the mean epithelial thickness (MET) of digestive tubules and enhanced reactive oxygen species (ROS) levels in haemolymph, while upon co-exposure the adverse impacts were alleviated. Real-time q-PCR results showed that most selected genes involved in stress response (FKBP, HSP90), immune (MyD88a, NF-κB) and detoxification (CYP4Y1) were induced for both single exposure and co-exposure. The co-presence of PS MPs down-regulated the mRNA expression of NF-κB in gills compared with of B[a]P alone. The uptake and toxicity reductions of B[a]P might result from the decrease of its bioavailable concentrations caused by the adsorption of B[a]P by PS MPs and the strong affinity of B[a]P to PS MPs. Adverse outcomes for the co-existence of marine emerging pollutants under long-term conditions remain to be further validated.

Identification and response of cytochrome P450 genes in the brackish water flea Diaphanosoma celebensis after exposure to benzo[α]pyrene and heavy metals

The cytochrome P450 (CYP) enzyme family is extensive; these enzymes participate in phase I enzyme metabolism and are involved in xenobiotic detoxification in all living organisms. Despite their significance in xenobiotic detoxification, little is known about the species-specific comparison of CYPs and their molecular responses in aquatic invertebrates. We identified 31 CYPs in the brackish water flea Diaphanosoma celebensis via thorough exploration of transcriptomic databases and measured the transcript profiles of 9 CYPs (within full sequences) in response to benzo[α]pyrene (B[α]P) and two heavy metals (cadmium [Cd] and copper [Cu]). Through phylogenetic analysis, the CYPs were separated and clustered into four clans: mitochondrial, CYP2, CYP3, and CYP4. The expression of 9 CYPs were differentially modulated (up- and/or downregulated) in response to B[α]P, Cd, and Cu. In particular, CYP370A15 was significantly upregulated in response to B[α]P, Cd, and Cu, suggesting that the identified CYPs are involved in xenobiotic detoxification and are useful as biomarkers in response to B[α]P, Cd, and Cu. This study aimed to comprehensively annotate cladoceran CYPs; our results will add to the existing knowledge on the potential roles of CYPs in xenobiotic detoxification in cladocerans.

Two novel CYP3A isoforms in marine mussel Mytilus coruscus: Identification and response to cadmium and benzo[a]pyrene

CYP3A enzymes play a crucial role in metabolic clearance of a variety of xenobiotics. However, their genetic information and function remain unclear in molluscs. In the present study, two novel CYP3A genes i.e. McCYP3A-1 and McCYP3A-2 were identified and characterized from the thick shell mussel Mytilus coruscus, and their tissue distribution as well as the response to cadmium (Cd) and benzo[a]pyrene (B[α]P) exposure were addressed using real time quantitative RT-PCR (qRT-PCR) and erythromycin N-demethylase (ERND) assay. McCYP3A-1 and McCYP3A-2 possess typically domains of CYP family such as helix-C, helix-I, helix-K, PERF and the heme binding domain as well as the characteristic domains of CYP3s including six SRS motifs. McCYP3A-1 and McCYP3A-2 transcripts were constitutively expressed in all examined tissues with high expression level in digestive glands, hepatopancreas and gonads. Upon B[α]P exposure, McCYP3A-1 and McCYP3A-2 mRNA expression in digestive glands showed a pattern of up-regulation followed by down-regulation, while under Cd exposure, showed a time-dependent induction profile. In addition, ERND activity, generally used as an indicator of CYP3, increased in a time-dependent manner after exposure to Cd and B[α]P. These results collectively indicated that McCYP3A-1 and McCYP3A-2 are CYP3A family member and may play a potential role in metabolic clearance of xenobiotics. Meanwhile, the current results may provide some baseline data to support McCYP3A-1 and McCYP3A-2 as candidate biomarkers for monitoring of PAHs and heavy metal pollution.

Marine copepod cytochrome P450 genes and their applications for molecular ecotoxicological studies in response to oil pollution

Recently, accidental spills of heavy oil have caused adverse effects in marine organisms. Oil pollution can induce damages on development and reproduction, linking with detrimental effects on diverse molecular levels of genes and proteins in plankton and fish. However, most information was mainly focused on marine vertebrates and consequently, limited information was available in marine invertebrates. Furthermore, there is still a lack of knowledge bridging in vivo endpoints with the functional regulation of cytochrome P450 (CYP) genes in response to oil spill pollution in marine invertebrates. In this paper, adverse effects of oil spill pollution in marine invertebrates are summarized with the importance of CYP genes as a potential biomarker, applying for environmental monitoring to detect oil spill using marine copepods.

A comparative proteomic study on the effects of metal pollution in oysters Crassostrea hongkongensis

The metal pollution has posed great risk on the coastal organisms along the Jiulongjiang Estuary in South China. In this work, two-dimensional electrophoresis-based proteomics was applied to the oysters Crassostrea hongkongensis from metal pollution sites to characterize the proteomic responses to metal pollution. Metal accumulation and proteomic responses indicated that the oysters from BJ site were more severely contaminated than those from FG site. Compared with those oyster samples from the clean site (JZ), metal pollution induced cellular injuries, oxidative and immune stresses in oyster heapatopancreas from both BJ and FG sites via differential metabolic pathways. In addition, metal pollution in BJ site induced disturbance in energy and lipid metabolisms in oysters. Results indicated that cathepsin L and ferritin GF1 might be the biomarkers of As and Fe in oyster C. hongkongensis, respectively. This study demonstrates that proteomics is a useful tool for investigating biological effects induced by metal pollution.

Upregulation of biotransformation genes in gills of oyster Crassostrea brasiliana exposed in situ to urban effluents, Florianópolis Bay, Southern Brazil

The release of untreated sanitary sewage, combined with unplanned urban growth, are major factors contributing to degradation of coastal ecosystems in developing countries, including Brazil. Sanitary sewage is a complex mixture of chemicals that can negatively affect aquatic organisms. The use of molecular biomarkers can help to understand and to monitor the biological effects elicited by contaminants. The aim of this study was to evaluate changes in transcript levels of genes related to xenobiotic biotransformation in the gills of oysters Crassostrea brasiliana transplanted and kept for 24h at three areas potentially contaminated by sanitary sewage (Bücheller river, BUC; Biguaçu river, BIG; and Ratones island, RAT), one farming area (Sambaqui beach, SAM) and at one reference site (Forte beach, FOR) in the North Bay of Santa Catarina Island (Florianópolis, Brazil). Transcript levels of four cytochrome P450 isoforms (CYP2AU1, CYP3A-like, CYP356A1-like and CYP20A1-like), three glutathione S-transferase (GST alpha-like, GST pi-like and GST microsomal 3-like) and one sulfotransferase gene (SULT-like) were evaluated by means of quantitative reverse transcription PCR (qRT-PCR). Chemical analysis of the sediment from each site were performed and revealed the presence of aliphatic and polycyclic aromatic hydrocarbons, linear alkylbenzenes and fecal sterols in the contaminated areas (BUC and BIG). Water quality analysis showed that these sites had the highest levels of fecal coliforms and other parameters evidencing the presence of urban sewage discharges. Among the results for gene transcription, CYP2AU1 and SULT-like levels were upregulated by 20 and 50-fold, respectively, in the oysters kept for 24h at the most contaminated site (BUC), suggesting a role of these genes in the detoxification of organic pollutants. These data reinforce that gills possibly have an important role in xenobiotic metabolism and highlight the use of C. brasiliana as a sentinel for monitoring environmental contamination in coastal regions.

Transcription of a novel P450 gene varies with some factors (pollutant exposure, temperature, time, and body region) in a marine oligochaete (Thalassodrilides sp.)

Cytochrome P450 (CYP) enzymes play important roles in the metabolism of exogenous compounds such as polycyclic aromatic hydrocarbons (PAHs). A novel, full-length CYP gene (CYP4V30) was identified in the oligochaete Thalassodrilides sp. CYP4V30 mRNA expression was studied in worms exposed to PAH-polluted (Σ16PAHs; 37441ng/g dry weight) or unpolluted (Σ16PAHs; 19ng/g dry weight) sediment. CYP4V30 expression was much higher in worms exposed to contaminated sediments than in those exposed to unpolluted sediments at some temperatures (20 and 25°C) and exposure durations (11-fold increase at 20°C, 10-day exposure), but not at 15°C or other exposure durations (P<0.05). CYP4V30 mRNA expression was higher in the middle of the body than in the posterior (P<0.05). The variation in transcriptional response with exposure time, temperature, and body region indicates that these factors should be considered when monitoring marine sediment pollution.

Identification of two isoforms of CYP4 in Marsupenaeus japonicus and their mRNA expression profile response to benzo[a]pyrene

CYP4 enzymes are essential components of cellular detoxification systems and play important roles in monitoring persistent organic pollutants in marine environments. However, there are few studies on CYP4 in shrimp. In this study, two CYP4 isoforms, CYP4V28 and CYP4V29, were cloned from Marsupenaeus japonicus for the first time, and the tissue distributions and mRNA expression profile in response to benzo[a]pyrene (B[a]P) were analyzed by quantitative real-time PCR (QRT-PCR). The full lengths of CYP4V28 and CYP4V29 were 1771 bp and 1647 bp respectively, with deduced amino acid sequences of 511 and 515 amino acids. The two CYP4s were predominantly expressed in the hepatopancreas and weakly expressed in other six tested tissues. As demonstrated by QRT-PCR, the mRNA levels of the two CYP4s show both a time- and dose-dependent response to B[a]P. The mRNA expression levels of CYP4V28 and CYP4V29 peaked at 12 h and 6 h respectively, and the peak level exhibited a tendency of positive correlation with the concentration of B[a]P. This study provides clues for further elucidating the function and regulation mechanisms of the two CYP4s in M. japonicas and evaluating of the biomarker potential of the two CYP4 isoforms.

Key metabolic pathways involved in xenobiotic biotransformation and stress responses revealed by transcriptomics of the mangrove oyster Crassostrea brasiliana

The Brazilian oyster Crassostrea brasiliana was challenged to three common environmental contaminants: phenanthrene, diesel fuel water-accommodated fraction (WAF) and domestic sewage. Total RNA was extracted from the gill and digestive gland, and cDNA libraries were sequenced using the 454 FLX platform. The assembled transcriptome resulted in ̃20,000 contigs, which were annotated to produce the first de novo transcriptome for C. brasiliana. Sequences were screened to identify genes potentially involved in the biotransformation of xenobiotics and associated antioxidant defence mechanisms. These gene families included those of the cytochrome P450 (CYP450), 70kDa heat shock, antioxidants, such as glutathione S-transferase, superoxide dismutase, catalase and also multi-drug resistance proteins. Analysis showed that the massive expansion of the CYP450 and HSP70 family due to gene duplication identified in the Crassostrea gigas genome also occurred in C. brasiliana, suggesting these processes form the base of the Crassostrea lineage. Preliminary expression analyses revealed several candidates biomarker genes that were up-regulated during each of the three treatments, suggesting the potential for environmental monitoring.

Expression and immunohistochemical localization of the cytochrome P450 isoform 356A1 (CYP356A1) in oyster Crassostrea gigas

Cytochrome P450 family (CYP) is a group of proteins virtually found in all living organisms. The main role of most CYPs is to metabolize endo and xenobiotics. Most of the studies on CYP have been carried out in mammals and other vertebrates, however recently a growing interest has been devoted to the identification of CYP isoforms in invertebrates. A gene belonging to the CYP sub-family, CYP356A1, was identified in sanitary sewage-exposed Pacific oysters, Crassostrea gigas. Through heterologous expression, we produced CYP356A1 purified protein and raised a mouse polyclonal antibody. Dot blot tests showed that oysters exposed in situ for 14 days to untreated urban effluent discharges had significantly higher levels of CYP356A1 in digestive gland. Using immunohistochemical techniques we observed that the lining epithelial cells of mantle, stomach and intestine showed a strong CYP356A1 staining, but the mucus and secretory cells were negative. Digestive diverticulum parenchyma and gills lining cells showed strong CYP356A1 reaction, while the filamentary rod (connective tissue) was negative. Free cells, as hemocytes and brown cells also showed CYP356A1 immunoreactions indicating the presence of biotransformation activity in these cells. Male germ cells at early stages expressed CYP356A1 but not sperm mature cells, suggesting that this protein could be involved in the male gonadal development. This study shows the use of a specific antibody to a mollusk CYP isoform and that this protein is inducible in oysters environmentally exposed to urban sewage effluents.

Response of detoxification gene mRNA expression and selection of molecular biomarkers in the clam Ruditapes philippinarum exposed to benzo[a]pyrene

Benzo[a]pyrene (B[a]P) has a high carcinogenic potential. B[a]P concentrations and molecular biomarkers (mRNA expressions of Pgp, AhR, CYP4, CYP414A1, GST-pi, GST-S2, Cu/Zn-SOD and Mn-SOD) were assayed in gills and digestive glands of the clam Ruditapes philippinarum exposed to 0.03, 0.3 and 3 μg/L B[a]P for 21 days and then exposed to natural seawater for 15 days. Results showed that B[a]P was rapidly accumulated in and then eliminated from tissues of the clams. All gene mRNA expressions in the treated groups were induced significantly with the exception of CYP414A1 and Cu/Zn-SOD in the 0.03 μg/L B[a]P group. According to correlation analysis, mRNA expressions of AhR, GST-pi and Mn-SOD in gills and GST-pi in digestive glands had good correlations with B[a]P concentrations and could be used as molecular biomarkers of B[a]P exposure. This study investigated the molecular response of the genes mentioned above and selected useful molecular biomarkers for B[a]P pollution monitoring.

Expression of three novel cytochrome P450 (CYP) and antioxidative genes from the polychaete, Perinereis nuntia exposed to water accommodated fraction (WAF) of Iranian crude oil and benzo[a]pyrene

To report a novel CYP genes and to evaluate its potency as a biomarker for oil pollution, we cloned three CYP genes and measured their expression profiles under controlled lab conditions using real-time reverse transcription PCR (real-time RT-PCR) after exposure of the water accommodated fraction (WAF) of Iranian crude oil and benzo[α]pyrene (B[α]P) as a positive control. Of these, CYP432A1 (CYP3 clan) gene was significantly induced by B[α]P exposure, indicating that the CYP3 clan gene would play an important role in polycyclic aromatic hydrocarbon (PAH) metabolisms, particularly for B[α]P in this species. However, the Perinereis nuntia CYP431A1 mRNA, a CYP2 clan gene, was sensitively expressed to WAF exposure with other two CYP genes. As one of Phase II detoxification enzymes, the glutathione S-transferase (GST) genes also upregulated with other antioxidant genes (SOD and CAT), indicating that WAF-exposed P. nuntia was properly responding to this kind of chemical stress. Thus, three CYP genes from the polychaete, P. nuntia have a potential as a biomarker in monitoring of the marine sediment after an oil spill accident.

Expression profile analysis of antioxidative stress and developmental pathway genes in the manganese-exposed intertidal copepod Tigriopus japonicus with 6K oligochip

Manganese (Mn) provides one of aquatic pollutants in marine ecosystem. Here we used a 6K oligomicroarray to identify the effect of Mn on transcriptomes in the copepod Tigriopus japonicus. A total of 5594 spots were significantly modulated on a 6K oligomicroarray with hierarchical clustering after exposure to Mn over 24h. Of them, 186 and 489 genes were significantly upregulated and downregulated, respectively. Particularly, several genes involved in stress, detoxification, and developmental functions were significantly modulated in T. japonicus exposed for 24h. In detail, Mn exposure specifically up-regulated genes that were related to intracellular stress, antioxidant, and detoxification pathways such as cytochrome P450s (CYPs), glutathione S-transferases (GSTs), and heat shock proteins (hsps), while a majority of downregulated genes was associated with developmental pathways such as cuticle protein, ecdysone receptor, and vitellogenin. These results demonstrated that Mn exposure modulated gene expression in relation to intracellular stress, leading to developmental retardation in the intertidal copepod, T. japonicus, and provide a better understanding of mechanistic molecular studies of Mn-induced cellular damage.